Method of forming a fabric covered cellulose sponge strand and then compressing it in a plurality of directions

ABSTRACT

A PROCESS FOR CONTINUOUS MANUFACTURE OF SHAPED VAGINAL TAMPONS OF REGENERATED CELLULOSE SPONGE MATERIAL COMPRISING EXTRUDING CELLULOSE SPONGE FORMING MATERIAL INTO A TUBULAR FABRIC CASING, REGENERATING, WASHING AND DRYING THE MATERIAL, DRAWING THE CASING THROUGH A HEATED TAPERING TUBUULAR PASSAGEWAY TO COMPRESS SAID STRAND IN A PLURALITY OF DIRECTIONS AND SEVERING THE STRAND INTO TAMPONS. THE COMPRESSED CELLULOSE SPONGE IS CAPABLE OF RESUMING ITS DIMENSIONS WHEN MOISTENED.

Apnl 24. 1973- o. T. JONES ET 3,129,537

METHOD OF FOBMIKG A FABRIC COVERED CELLULOSE SPONGE 5TRAND AND THEN CQMPRESSING IT IN A PLURALITY OF DIRECTIONS Original Filed July 12. 1968 United States Patent Oflice 3,729,537 Patented Apr. 24, 1973 3,729,537 METHOD OF FORMING A FABRIC COVERED CELLULOSE SPONGE STRAND AND THEN COMPRESSING IT IN A PLURALITY OF DIRECTIONS David Thomas Jones and George Edward Jowett, Swansea, Glamorgan, Wales, and Edward Ernest Webster, Orpington, Kent, England, assignors to Sponcel Limited, Croydon, Surrey, England Continuation of abandoned application Ser. No. 744,535, July 12, 1968. This application Aug. 26, 1970, Ser. No. 67,241 Claims priority, application Great Britain, July 19, 1967, 33,095/ 67 Int. Cl. B29d 27/04 US. Cl. 264-47 4 Claims ABSTRACT OF THE DISCLOSURE A process for continuous manufacture of shaped vaginal tampons of regenerated cellulose sponge material comprising extruding cellulose sponge forming material into a tubular fabric casing, regenerating, washing and drying the material, drawing the casing through a heated tapering tubular passageway to compress said strand in a plurality of directions and severing the strand into tampons. The compressed cellulose sponge is capable of resuming its dimensions when moistened.

This application is a continuation of our prior application Ser. No. 744,535, filed July 12, 1968, and now abandoned.

This invention concerns improvements in and relating to the manufacture of regenerated cellulose sponge material, and relates more especially to a process for the production of an elongated web or rope of regenerated cellulose sponge material having a relatively small crosssection of predetermined shape.

Regenerated cellulose sponge is conventionally produced by placing in a metal mould a mixture of viscose paste and sodium sulphate or other crystals with or without reinforcing fibres of hemp, flax or other material, and regenerating the cellulose from the viscose by heat and/or chemical action. The crystals are removed by heating or by subsequent washing processes, thus leaving a porous mass absorbent to aqueous solutions. This process is suitable for producing relatively large blocks of sponge material, pieces of sponge required to be of dimensions approximately 2 inches square or less being obtained by cutting from the larger blocks.

The present invention provides a process for the production of regenerated cellulose sponge material in strip form, wherein a sponge forming mixture comprising viscose paste is extruded into a flexible tubular reinforcing outer casing to form a web or rope of paste supported in said casing, and regeneration of the viscose paste is effected whilst maintaining the desired final cross-sectional shape of said web or rope.

The said outer casing may be removed after regeneration of the sponge material, so that the final sponge is left without external reinforcement, or may be left permanently in place as an outer reinforcing layer of the sponge. In the former case the casing may comprise a membrane or film of suitable material, for example those polyolefines and other plastics which withstand the temperature at which regeneration is carried out, certain cellulose casings, polytetrafiuorethylene and the like. In the latter case the casing may comprise a knitted or woven fabric capable of becoming permanently bonded to the sponge material during the regeneration process. Such a knitted fabric could be formed in situ by a circular knitting machine arranged round the extrusion nozzle. The casing may be seamless, for example an extruded tubular film or a circularly knitted fabric, or may be formed by seaming a fiat web into the form of a tube. Also a flat web may be applied directly to the extruded paste, without seaming of the web, by folding the web around the extrusion nozzle in a continuous manner so that the web is drawn from the nozzle in the form of a continuous folded tube.

The process according to the present invention has the advantage that strips of regenerated cellulose sponge of relatively small cross-section can be produced in crosssectional shapes that would be difficult to achieve by conventional means, for example by cutting from larger moulded blocks of sponge. Moreover such strips may have a woven or knitted outer reinforcing covering bonded securely thereto during the regeneration process.

Strip sponge material so produced is very useful for the production of articles such as catamenial tampons.

According to one embodiment of the invention, extrusion of the said mixture into the outer casing may be effected by extruding the mixture from a nozzle extending in the form of a pipe or horn, the casing being arranged in longitudinally collapsed form around the outer circumference of the pipe so that the pasty mixture issuing from the extrusion orifice fills the casing and draws the same from around the extrusion nozzle. Uniform filling of the casing may be promoted by applying frictional contact with the outer surface of the casing, either manually or by an annular restraining means, in order to provide slight resistance to withdrawal of the casing from the nozzle. The extrusion nozzle may incorporate a magazine in the form of a turret or sliding plate having a plurality of pipe or horn members for successive registration with an extrusion die in order to effect rapid changeover of outer casings as they become exhausted.

The web or rope may be shaped to the desired final cross-sectional shape, for example circular, rectangular or oval, prior to or during regeneration of the paste, for example by a member in the form of a sleeve of the desired cross-section through which the filled outer casing is arranged to pass, or by a pair of appropriately shaped nip rollers. When the desired final shape is circular, such a shaping means may in some cases be rendered unnecessary.

According to a further embodiment of the invention the sponge material produced by the above described method may be dried and compressed to cross-sectional dimensions substantially less than those in its moist relaxed state. This can be achieved by heating the material with hot air or other means and subsequently compressing it between heated platens or one or more pairs of rollers. The rollers or platens may be shaped to impart a desired cross-sectional shape to the compressed sponge. Alternatively, a particularly advantageous method of compressing the sponge material is by drawing it through a heated, tapering, tubular former. When re-moistened, the compressed sponge material in known manner regains its original dimensions in the moist relaxed state.

The sponge material may be cut into pieces of the desired length either before or after compression.

The invention is illustrated by way of example in the accompanying drawing, in which:

FIG. 1 is an elevation, in diagrammatic form of an arrangement for carrying out the process according to the invention,

FIG. 2 is a sectional elevation showing a restraining means for retaining a supply of outer reinforcing casing around an extrusion nozzle,

FIG. 3 is a section on the line III-III of FIG. 1, showing the shaping rollers for the web or rope of paste, and

FIG. 4 is an elevation, partly in section, of an arrangement for compression of the regenerated sponge strip.

Referring to FIG. 1 of the drawings a positive displacement extrusion pump 1, has an extrusion nozzle in the form of a pipe 2 around which is arranged a supply of shirred tubular reinforcing casing 3 for a web or rope 4 of viscose paste to be extruded. The rope 4 is formed by extruding the paste of viscose containing reinforcing fibres and pore forming crystals into the casing 3 so that it draws the latter from the nozzle 2. The casing 3 is held onto the nozzle, either manually or by a restraining ring 5 of nylon or like material (see FIG. 2), so that there is slight resistance to withdrawal of the casing from the nozzle 2 and the casing is uniformly filled with paste. The rope 4 is passed directly into a conventional coagulating bath 6 referred to below, and then between two pairs of shaping rollers 7 at the surface of the bath. Between the pairs of rollers 7 and above the bath 6 is arranged an auxiliary spray bath 8 for spraying the upper side of the rope 4 with coagulating liquid. The rope 4 is finally removed from the bath 6 over a transfer roller 9.

The arrangement of the coagulating bath 6, rollers 7 and auxiliary spray bath 8 is such that at the point where the rope 4 meets the first pair of rollers it is partially regenerated, but is still capable of being shaped by the rollers 7. In this way the necessity for imparting a given cross-section to the rope 4 at the time of extrusion is avoided, unless the final shape departs radically from the extruded cross-section. As shown in FIG. 3, the rollers 7 are arranged to impart an elliptical final shape to the rope 4. Any other desired shape, for example a circular or rectangular cross section, may be imparted to the rope 4 in like manner.

A convenient method of estimating the point at which the rope 4 should be formed by the rollers 7 is as follows. When the viscose paste rope 4, is extruded directly into the bath 6 it initially sinks, owing to the fact that the mixture of paste and crystals is heavier than the liquid of the bath 6. As the crystals melt, however, the rope 4 becomes gradually lighter until it floats on the surface of the bath. By arranging the first pair of rollers 7 at the point where the rope 4 floats, efiective shaping of the latter can be carried out at this point. The fact that the rope 4 is supported on the surface of the liquid between the spaced pairs of rollers 7 is an assistance in maintaining the shape of the rope during final regeneration thereof. The spray bath 8 serves to supply coagulating liquid to the upper exposed side of the rope 4. The rollers 7 may either be driven rollers or idler rollers.

The rope 4 may be formed of a conventional viscose paste sponge forming mix containing reinforcing fibres and pore forming crystals such as sodium sulphate crystals, the grade of mix preferably being such as to form a fine pore sponge. The outer casing 3 is a woven fabric such that it becomes permanently bonded with the surface of the sponge. Suitable regeneration baths are illustrated in the following examples.

EXAMPLE 1 A rope of viscose paste as described above was formed by extrusion into a shirred tubular casing of woven cotton stockinet. The rope was passed directly into a liquid coagulating bath as described above and having a length of 40 feet. The bath was a heat regenerating bath comprising a solution of sodium sulphate at a temperature of 95 C. The extrusion rate of the rope and the corresponding rate of passage through the bath was 3 ft. per minute.

EXAMPLE 2 The process of Example 1 was repeated, with an extruded rope formed by extrusion into an impermeable outer casing of polypropylene. In order to enable complete regeneration of the rope using the same bath, the extrusion rate was reduced to 1 ft. per minute.

EXAMPLE 3 An extruded rope was formed as described above by extrusion of a viscose paste mixture into an outer casing of woven cotton stockinet, and passed into a coagulating bath as described above and 40 ft. long. The coagulating bath was an acid coagulating bath comprising a 3-5% solution of sulphuric acid with 500-700 grams per litre of Glaubers salt in solution at a temperature of 85 C. The extrusion rate was 2-3 ft. per minute.

In the process described above, advantageously a plurality of ropes as described are extruded simultaneously from adjacent extrusion nozzles and are passed through a common coagulating bath. Each extrusion pump preferably has a turret arrangement comprising a plurality of extrusion nozzles that can be interchanged to enable quick recharging of a supply of casing. This enables the process to be carried out continuously.

According to a modification of the above arrangement, not shown, regeneration of the viscose paste is effected with the said web or rope freely suspended in a vertical position. The web or rope is then self supporting in the desired cross sectional shape. Thus the sponge mixture may be extruded in a vertically upward or downward direction, into the tubular casing, the web or rope formed by the casing together with the sponge mixture being drawn from the extrusion nozzle by means of take up rollers located vertically above or below the nozzle and spaced therefrom, and that portion of the web or rope located between the extrusion nozzle and the take up rollers being subjected to a regeneration process so that the viscose paste becomes substantially completely regenerated to cellulose by the time the web or rope meets the take up rollers. The take up rollers may be in the form of pulleys as described above defining between them the desired cross-sectional shape of the web or rope. If desired the web or rope may be guided by further similar take up rollers before and/or during regeneration of the viscose, the rollers serving to form or re-establish the desired cross-section of the web or rope whilst at the same time serving to transport and/or change the direction of movement of the web or rope. In this way the extrusion of the web or rope may be carried out in a horizontal direction and the web or rope may be subsequently transported in a vertical direction by said rollers.

After regeneration the cellulose sponge material is set in its final form and may be transported in any convenient manner to the conventional finishing and rinsing baths. The sponge may further be passed through baths of other solutions for the purpose of impregnating the sponge, for example with solutions of medicaments, humidifying agents, deodorants, odour producing substances, or preservatives for combatting attack by bacteria or fungi.

For example the sponge may be treated with a 0.1 solution of Cetrimide which when the sponge is dried comprises 0.l0.2 of the dry weight of the sponge. This gives an increased wetting rate of the dry sponge, and also acts as a bacteriocide.

After regeneration, and after treatment of the sponge as described above, it may be dried by means of hot air and compressed to cross-sectional dimensions substantially less than those in its moist relaxed state. This can be done in known manner by means of heated pressure platens. However a means particularly suited to the novel sponge rope formed in accordance with the invention is shown in FIG. 4. This comprises a tapering tubular stainless steel former 10 having a general cross-section corresponding to that of the rope 4. The former has an annular external recess 10a in which is arranged an electrical resistance heating element 11 closely surrounding the tapering wall of the former 10. The remainder of the recess 10a is filled with the heat insulating material 12, and the whole is closed by a cylindrical cover 13. In

order to compress the rope 4, it is drawn through the former 10 in the direction of the arrow A so that the heated tapering walls of the former effect compression of the sponge. The outer reinforcing covering of the sponge serves to prevent breakage thereof under tension.

The angle of taper of the former 10 should be selected by experiment to provide effective compression of the sponge without the necessity of undue tension thereon.

It has been found for example that a former -6 inches long is required to effect compression of a sponge from 1 inch to /2 inch in diameter.

The optimum temperature of the former for the effective compression of the sponge material is in the region of 130-150 C., the corresponding rate of throughput of the sponge material being adjusted by experiment.

We claim:

1. A process for the manufacture of shaped vaginal tampons of regenerated cellulose sponge material, which process comprises the steps of continuously extruding a sponge-forming material into a circumferentially continuous and flexible tubular reinforcing outer fabric casing to form said material into an elongated strand,

regenerating, Washing and drying said material,

drawing the resulting regenerated cellulose sponge strand within said casing through a heated tapering tubular passageway and thereby simultaneously compressing said strand in a plurality of directions at right angles to its longitudinal axis to produce a strand which is expansible on moistening to resume dimensions corresponding to those of the uncompressed strand, and

severing said strand into tampons.

2. A process according to claim 1, which comprises the 3 step of extruding said mixture into the outer casing through a nozzle having an extension in the form of a tubular pipe, and arranging the casing in longitudinally collapsed form around the outer circumference of the pipe so that the material issuing from the extrusion nozzle fills the casing and draws the said casing from around the extrusion nozzle.

3. A process according to claim 1, wherein the sponge forming material is formed before drying into a crosssectional shape different from that in which it is extruded.

4. A process according to claim 1 in which said sponge forming material is regenerated while maintaining said strand in a given cross-sectional shape and in which said strand is supported solely by said casing.

References Cited UNITED STATES PATENTS 3,382,303 5/1968 Stieg 26449 2,9 13 ,772 11/ 9 Buchkremer 264-49 3,399,423 9/1968 Kielsmeier 17-35 3,414,936 12/ 1968 Lugiewicz 1740 2,827,661 3/ 1958 Vonkohorn 26449 X 3,377,652 4/1968 Politzer 26449 X 3,048,888 8/ 1962 Shockley 26449 3,486,191 12/ 1969 Bibo'st 26449 2,670,500 3/ 1954 Ensslin 26449 FOREIGN PATENTS 114,829 6/ 1942 Australia 264321 5,234 3/1965 Japan 26447 DONALD J. ARNOLD, Primary Examiner P. A. LEIPOLD, Assistant Examiner US. Cl. X.R. 

